Add Python debugging section

.gitignore

@@ -11,6 +11,7 @@
 /var
 
 # File names:
+buggy.py
 column-view-demonstration.org
 custom.el
 dir-locals.el

README.org

@@ -6141,6 +6141,28 @@ configures =code-cells=.
       (keymap-set map "C-c C-c" #'code-cells-eval))))
 #+end_src
 
+*** [[https://stackoverflow.com/questions/2324758/debugging-python-programs-in-emacs][Debugging Python programs in Emacs]]
+:PROPERTIES:
+:CUSTOM_ID: sec:debug-python
+:END:
+
+Listing [[lst:pdb-example]] shows how to start using PDB.  Links of interest are:
+- [[https://realpython.com/python-debugging-pdb/][Python Debugging with PDB]]
+- [[https://docs.python.org/3/library/pdb.html][The Python Debugger]]
+- [[yt:vfPtGsSJldg][Introduction to PDB (Python-2.7 YouTube video)]]
+
+#+caption[PDB example: =python -m pdb .emacs.d/buggy.py=]:
+#+caption: PDB example: =python -m pdb .emacs.d/buggy.py=.
+#+name: lst:pdb-example
+#+begin_src python -i -n :results silent :tangle buggy.py
+def unsafe(x, y):
+    """Raises an exception if the second argument equals zero."""
+    return x / y
+
+if __name__ == "__main__":
+    unsafe(1.0, 0.0)
+#+end_src
+
 * [[https://github.com/emacs-tw/awesome-emacs#library][Libraries]]
 :PROPERTIES:
 :CUSTOM_ID: sec:libraries